Home About us Contact
|
Home About us Contact | ||
|
|
||
Selected Regions (selected + regions)
Selected AbstractsUncertainty and Sensitivity Analysis of Damage Identification Results Obtained Using Finite Element Model UpdatingCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2009Babak Moaveni The shake table tests were designed so as to damage the building progressively through several historical seismic motions reproduced on the shake table. A sensitivity-based finite element (FE) model updating method was used to identify damage in the building. The estimation uncertainty in the damage identification results was observed to be significant, which motivated the authors to perform, through numerical simulation, an uncertainty analysis on a set of damage identification results. This study investigates systematically the performance of FE model updating for damage identification. The damaged structure is simulated numerically through a change in stiffness in selected regions of a FE model of the shear wall test structure. The uncertainty of the identified damage (location and extent) due to variability of five input factors is quantified through analysis-of-variance (ANOVA) and meta-modeling. These five input factors are: (1,3) level of uncertainty in the (identified) modal parameters of each of the first three longitudinal modes, (4) spatial density of measurements (number of sensors), and (5) mesh size in the FE model used in the FE model updating procedure (a type of modeling error). A full factorial design of experiments is considered for these five input factors. In addition to ANOVA and meta-modeling, this study investigates the one-at-a-time sensitivity analysis of the identified damage to the level of uncertainty in the identified modal parameters of the first three longitudinal modes. The results of this investigation demonstrate that the level of confidence in the damage identification results obtained through FE model updating, is a function of not only the level of uncertainty in the identified modal parameters, but also choices made in the design of experiments (e.g., spatial density of measurements) and modeling errors (e.g., mesh size). Therefore, the experiments can be designed so that the more influential input factors (to the total uncertainty/variability of the damage identification results) are set at optimum levels so as to yield more accurate damage identification results. [source] How Does Structural Reform Affect Regional Development?ECONOMIC GEOGRAPHY, Issue 4 2000Resolving Contradictory Theory with Evidence from India Abstract: Regional theory offers little coherent guidance on the prospects for interregional development after structural reform in developing nations. In this paper I suggest a basic set of hypotheses in which the neoliberal nation-state is simultaneously a reduced state (less concerned about promoting regional balance) and an enlarged state (directing development toward selected regions). Under the new regulatory structure the location of post-reform investments may be expected to favor the coast, advanced regions, and existing metropolises (especially the edge areas); these expectations may be more true for foreign direct investments than domestic investments (especially the direct investments of the state). I use disaggregated pre- and post-reform industrial data from India to test the hypotheses. The results offer partial to full support for all hypotheses, providing evidence of the return of cumulative causation, and raising concerns about the political economy of future development in the lagging regions. [source] Analyzing brain networks with PCA and conditional Granger causalityHUMAN BRAIN MAPPING, Issue 7 2009Zhenyu Zhou Abstract Identifying directional influences in anatomical and functional circuits presents one of the greatest challenges for understanding neural computations in the brain. Granger causality mapping (GCM) derived from vector autoregressive models of data has been employed for this purpose, revealing complex temporal and spatial dynamics underlying cognitive processes. However, the traditional GCM methods are computationally expensive, as signals from thousands of voxels within selected regions of interest (ROIs) are individually processed, and being based on pairwise Granger causality, they lack the ability to distinguish direct from indirect connectivity among brain regions. In this work a new algorithm called PCA based conditional GCM is proposed to overcome these problems. The algorithm implements the following two procedures: (i) dimensionality reduction in ROIs of interest with principle component analysis (PCA), and (ii) estimation of the direct causal influences in local brain networks, using conditional Granger causality. Our results show that the proposed method achieves greater accuracy in detecting network connectivity than the commonly used pairwise Granger causality method. Furthermore, the use of PCA components in conjunction with conditional GCM greatly reduces the computational cost relative to the use of individual voxel time series. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [source] Multi-annual dry episodes in Australian climatic variabilityINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2009B. G. Hunt Abstract The output from a 10 000-year simulation with the CSIRO Mark 2 coupled global climatic model has been analysed to investigate the occurrence of multi-year dry episodes for three selected regions of Australia, specifically, the northeast, southeast and southwest of the continent. Results are presented for dry episodes lasting for 8 or more years. An episode is defined as a time interval having consecutive negative rainfall anomalies, but not necessarily a major drought, for each year of the episode. The hydrological consequences of such an episode can persist for over a century. Typically about 30 episodes are found over the 10 000 years of the simulation for each of the three regions. There is little synchronicity between the regions in the occurrence of the dry episodes. While there is an El Nino/Southern Oscillation (ENSO) influence associated with these episodes, it is not continuous over the duration of an episode. Composites of sea surface temperature anomalies over an episode highlight the limited presence of ENSO events. The occurrence of the dry episodes for all three regions is essentially random, with multi-centennial periods without an episode, and episodes at multi-decadal frequency at other times. Following a discussion of possible mechanistic influences, it is concluded that stochastic forcing is responsible for the occurrence of dry episodes. This implies that there is no predictability associated with the initiation, duration or termination of individual dry episodes. This also suggests that the 2000,2007 dry episodes occurring over much of Australia may not be caused by the greenhouse effect. Such an episode has a return period of between 200 and 300 years based on the mean frequency of occurrence in the present simulation. Copyright © 2008 Royal Meteorological Society [source] Regional cerebral glucose metabolism during sevoflurane anaesthesia in healthy subjects studied with positron emission tomographyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2010L. SCHLÜNZEN Background: The precise mechanism by which sevoflurane exerts its effects in the human brain remains unknown. In the present study, we quantified the effects of sevoflurane on regional cerebral glucose metabolism (rGMR) in the human brain measured with positron emission tomography. Methods: Eight volunteers underwent two dynamic 18F-fluorodeoxyglucose positron emission tomography (PET) scans. One scan assessed conscious-baseline metabolism and the other scan assessed metabolism during 1 minimum alveolar concentration (MAC) sevoflurane anaesthesia. Cardiovascular and respiratory parameters were monitored and bispectral index responses were registered. Statistical parametric maps and conventional regions of interest analysis were used to determine rGMR differences. Results: All subjects were unconsciousness at 1.0 MAC sevoflurane. Cardiovascular and respiratory parameters were constant over time. In the awake state, rGMR ranged from 0.24 to 0.35 ,mol/g/min in the selected regions. Compared with the conscious state, total GMR decreased 56% in sevoflurane anaesthesia. In white and grey matter, GMR was averaged 42% and 58% of normal, respectively. Sevoflurane reduced the absolute rGMR in all selected areas by 48,71% of the baseline (P,0.01), with the most significant reductions in the lingual gyrus (71%), occipital lobe in general (68%) and thalamus (63%). No increases in rGMR were observed. Conclusions: Sevoflurane caused a global whole-brain metabolic reduction of GMR in all regions of the human brain, with the most marked metabolic suppression in the lingual gyrus, thalamus and occipital lobe. [source] Bone marrow changes in adolescent girls with anorexia nervosaJOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2010Kirsten Ecklund Abstract Early osteoporosis is common among adolescent girls with anorexia nervosa (AN) and may result from premature conversion of red (RM) to yellow bone marrow. We performed right knee magnetic resonance imaging (MRI) on a 1.0 T extremity scanner in 20 patients and 20 healthy controls, aged 16.2,±,1.6 years (mean,±,SD). Coronal T1 -weighted (T1W) images and T1 maps were generated from T1 relaxometry images. Blinded radiologists visually assessed RM in the distal femoral and proximal tibial metaphyses in T1W images using a scale of signal intensity from 0 (homogeneous hyperintensity, no RM) to 4 (all dark, complete RM). Subjects with AN exhibited nearly twofold lower metaphyseal RM scores in both the femur (0.64 versus 1.22, p,=,.03) and tibia (0.54 versus 0.96, p,=,.08). In relaxometric measurements of four selected regions (femur and tibia amd epiphysis and metaphysis), subjects with AN showed higher mean epiphyseal but lower metaphyseal T1. The net AN-control difference between epiphysis and metaphysis was 70,ms in the femur (+31 versus ,35,ms, p,=,.02) and of smaller magnitude in the tibia. In relaxometry data from the full width of the femur adjacent to the growth plate, AN subjects showed mean T1 consistently lower than in controls by 30 to 50,ms in virtually every part of the sampling region. These findings suggest that adolescents with AN exhibit premature conversion of hematopoietic to fat cells in the marrow of the peripheral skeleton potentially owing to adipocyte over osteoblast differentiation in the mesenchymal stem cell pool. © 2010 American Society for Bone and Mineral Research [source] Sonographic examination of the oral phase of swallowing: Bolus image enhancementJOURNAL OF CLINICAL ULTRASOUND, Issue 2 2002Michael J. Casas DDS Abstract Purpose The purpose of this study was to evaluate the ability of 4 liquid boluses to enhance pixel brightness and the ease with which the boluses could be identified during the sonographic evaluation of oral swallowing in healthy young adults. Methods Ten healthy adult volunteers (5 men and 5 women), ranging in age from 21 to 31 years, underwent sonographic evaluation of the oral phase of swallowing while sitting in their usual feeding position. We compared the ability of the 4 following liquids to improve sonographic visualization of swallowing with that of water: a carbonated cola beverage, 5.0 ml of Thick-It in 120 ml of water, 2.5 ml of Thick-It in 120 ml of water, and 7.5 ml of confectioners' sugar in 120 ml of water. Water was used as a control. In each case, 5 ml of the liquid was introduced into the subject's oral cavity using a syringe, and the subject was instructed to swallow. Digitized still images and recorded video sequences of sonographic examinations of the swallowing were analyzed. The brightness of the bolus image on selected digitized video frames was measured digitally using Image Analyst software. Pixel brightness within selected regions of interest for each of the test liquids was statistically compared with that for water. Seven clinicians rated the visualization of each test liquid and water on paired sonographic videotape sequences. These ratings and the level of agreement between them were statistically tested. Results Only the carbonated cola beverage demonstrated statistically greater pixel brightness than that of water on digitized video frames (p = 0.01), whereas both cola (with a moderate inter-rater agreement, , = 0.50) and 5.0 ml Thick-It mixed with 120 ml of water (with a fair inter-rater agreement, , = 0.24) were significantly better visualized on sonographic video sequences. Conclusions The digital still-frame analysis confirmed the clinicians' ratings of bolus visualization on real-time sonography, but dynamic sonography is more important than still frames in assessing sonographic swallow media because the dynamic images more closely parallel what is seen in clinical practice. Future investigations of sonographic contrast agents for use in the examination of the oral phase of swallowing should use both static digital (still-frame) and dynamic (real-time) assessment methods, as well as expert reviewers. © 2002 John Wiley & Sons, Inc. J Clin Ultrasound 30:83,87, 2002; DOI 10.1002/jcu.10034 [source] Measurement of deep gray matter perfusion using a segmented true,fast imaging with steady-state precession (True-FISP) arterial spin-labeling (ASL) method at 3TJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2009Elan J. Grossman MS Abstract Purpose To study the feasibility of using the MRI technique of segmented true,fast imaging with steady-state precession arterial spin-labeling (True-FISP ASL) for the noninvasive measurement and quantification of local perfusion in cerebral deep gray matter at 3T. Materials and Methods A flow-sensitive alternating inversion-recovery (FAIR) ASL perfusion preparation was used in which the echo-planar imaging (EPI) readout was replaced with a segmented True-FISP data acquisition strategy. The absolute perfusion for six selected regions of deep gray matter (left and right thalamus, putamen, and caudate) were calculated in 11 healthy human subjects (six male, five female; mean age = 35.5 years ± 9.9). Results Preliminary measurements of the average absolute perfusion values at the six selected regions of deep gray matter are in agreement with published values for mean absolute cerebral blood flow (CBF) baselines acquired from healthy volunteers using positron emission tomography (PET). Conclusion Segmented True-FISP ASL is a practical and quantitative technique suitable to measure local tissue perfusion in cerebral deep gray matter at a high spatial resolution without the susceptibility artifacts commonly associated with EPI-based methods of ASL. J. Magn. Reson. Imaging 2009;29:1425,1431. © 2009 Wiley-Liss, Inc. [source] Mapping and characterization of B cell linear epitopes in the conservative regions of hepatitis C virus envelope glycoproteinsJOURNAL OF VIRAL HEPATITIS, Issue 3 2002L. V. Olenina Forty-eight overlapping octapeptides covering highly conservative regions of E1 and E2 hepatitis C virus (HCV) envelope proteins were synthesized and tested by ELISA against different groups of sera obtained from HCV-infected patients. All sera from patients with acute infection, except a single case of serum reactivity with the region HINRTALN, were nonreactive with any peptide. Sera obtained from chronic patients reacted with 12 peptides from five selected regions. Two immunodominant B epitopes were found, one being the precisely mapped antigenic site RMAWDM positioned inside the earlier shown immunodominant epitope from E1, and the second site, PALSTGLIH from E2, detected for the first time. New minor antigenic site was determined as PTDCFRKH from E2. We found only minor seroreactivity for one of the putative sites involved in CD81 binding, PYCWHYAP. [source] High-resolution NMR correlation experiments in a single measurement (HR-PANACEA)MAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2010riks Kup Abstract Three important NMR pulse sequences, INADEQUATE, HSQC and three-dimensional HMBC have been combined into a single entity called high-resolution Parallel Acquisition NMR: an All-in-one Combination of Experimental Applications (HR-PANACEA) to provide reliable structural information about a small molecule in a single measurement. This exploits a recent instrumental development that permits simultaneous acquisition of signals from several nuclear species, using multiple receivers. Where high-precision values of the long-range heteronuclear splittings are important, selected regions of a large experimental data matrix are extracted and examined with the highest possible resolution. The J -doubling technique is then applied to derive precise values for these couplings. As proof of principle, the method is applied to the molecule of methyl salicylate, confirming the expected conformation of the COH moiety. Copyright © 2010 John Wiley & Sons, Ltd. [source] An ATCA radio-continuum study of the Small Magellanic Cloud , IV.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006A multifrequency analysis of the N 66 region ABSTRACT Traditional identification of supernova remnants (SNRs) include the use of radio spectral index, optical spectral studies (including strong [S ii], [N ii], [O i], [O ii] and [O iii] lines) and X-ray co-identifications. Each of these can have significant limitations within the context of a particular SNR candidate and new identification methods are continually sought. In this paper, we explore subtraction techniques by Ye, Turtle and Kennicutt to remove thermal emission estimated from H, flux from radio-continuum images. The remaining non-thermal emission allows the identification of SNRs embedded within these H ii regions. Subtraction images of the N 66 region in the Small Magellanic Cloud (SMC) using H, wide-field optical CCD images from the Curtis Schmidt Telescope and the recent Australia Telescope Compact Array (ATCA)/Parkes radio-continuum (1420, 2370, 4800 and 8640 MHz) data are presented as an example. These show three SNRs (B0057 , 724, B0056 , 724 and B0056 , 725) separated from their surrounding H ii radio emission. 2.3-m dual-beam spectrograph long-slit spectra from selected regions within N 66 suggest the presence of an additional SNR with no radio or X-ray emission. Radio spectral index, [S ii]/H, ratio and archived Chandra images of N 66 combine to give a more coherent picture of this region, confirming B0057 , 724 as an SNR. The N 66 nebula complex is divided into 10 components, composed separately of these SNRs and H ii regions. [source] The value of observations.THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 628 2007III: Influence of weather regimes on targeting Abstract This paper assesses the value of targeted observations over the North Atlantic Ocean for different meteorological flow regimes. It shows that during tropical cyclone activity and particularly tropical cyclone transition to extratropical characteristics, removing observations in sensitive regions, indicated by singular vectors optimized on the 2-day forecast over Europe, degrades the skill of a given forecast more so than excluding observations in randomly selected regions. The maximum downstream degradation computed in terms of spatially and temporally averaged root-mean-square error of 500 hPa geopotential height is about 13%, a value which is 6 times larger than when removing observations in randomly selected areas. The forecast impact for these selected periods, resulting from degrading the observational coverage in sensitive areas, was similar to the impact found (elsewhere in other weather forecast systems) for the observational targeting campaigns carried out over recent years, and it was larger than the average impact obtained by considering a larger set of cases covering various seasons. Copyright © 2007 Royal Meteorological Society [source] Glycerol-induced folding of unstructured disulfide-deficient lysozyme into a native-like conformationBIOPOLYMERS, Issue 8 2009Keiko Sakamoto Abstract 2SS[6-127,64-80] variant of lysozyme which has two disulfide bridges, Cys6-Cys127 and Cys64-Cys80, and lacks the other two disulfide bridges, Cys30-Cys115 and Cys76-Cys94, was quite unstructured in water, but a part of the polypeptide chain was gradually frozen into a native-like conformation with increasing glycerol concentration. It was monitored from the protection factors of amide hydrogens against H/D exchange. In solution containing various concentrations of glycerol, H/D exchange reactions were carried out at pH* 3.0 and 4°C. Then, 1H- 15N-HSQC spectra of partially deuterated protein were measured in a quenching buffer for H/D exchange (95% DMSO/5% D2O mixture at pH* 5.5 adjusted with dichloroacetate). In a solution of 10% glycerol, the protection factors were nearly equal to 10 at most of residues. With increasing glycerol concentration, some selected regions were further protected, and their protection factors reached about a 1000 in 30% glycerol solution. The highly protected residues were included in A-, B-, and C-helices and ,3-strand, and especially centered on Ile 55 and Leu 56. In 2SS[6-127,64-80], long-range interactions were recovered due to the preferential hydration by glycerol in the hydrophobic box of the ,-domain. Glycerol-induced recovering of the native-like structure is discussed from the viewpoint of molten globules growing with the protein folding. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 665,675, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Incidence of severe pre-eclampsia, postpartum haemorrhage and sepsis as a surrogate marker for severe maternal morbidity in a European population-based study: the MOMS-B surveyBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 1 2005Wei-Hong Zhang Objective To describe the incidence of three conditions of acute severe maternal morbidity in selected regions in nine European countries. Design A population-based questionnaire survey. Setting Eleven regions in nine countries of Europe. Population All the pregnant women in each region who had delivered during the period covered by the study. Methods Standard definitions of three severe obstetric conditions, pre-eclampsia, postpartum haemorrhage and sepsis were established by a steering committee. A common questionnaire was used in each participating country. The incidence of the three obstetric conditions and characteristics of the study women were compared. Main outcome measures Incidence of three severe obstetric conditions: pre-eclampsia, postpartum haemorrhage and sepsis. Results The study identified 1734 women with at least one of the three conditions, with 847 experiencing severe haemorrhage, 793 experiencing severe pre-eclampsia and 142 experiencing severe sepsis. There were wide variations in incidence of three conditions combined, ranging from 14.7 per thousand deliveries in Brussels, Belgium to 6.0 per thousand deliveries in Upper Austria. Conclusions This study sets a simple and straightforward approach to the definition of three severe obstetric conditions and allows population-based comparisons between developed countries in Europe, even though difficulties may have been present with applying the definition across countries. The reported incidence of these severe obstetric conditions in general and severe haemorrhage varied significantly between countries. Overall, severe haemorrhage in particular was the most common of the three conditions, followed closely by severe pre-eclampsia. [source] | ||||||||||||||||